Thrombospondin-1 (TSP-1) up-regulates tissue inhibitor of metalloproteinase-1 (TIMP-1) production in human tumor cells: Exploring the functional significance in tumor cell invasion

Thrombospondin-1 (TSP-1), a matrix-bound adhesive glycoprotein, has been shown to modulate tumor progression. We previously demonstrated that TSP-1 up-regulates matrix metalloproteinases MMP-2 and MMP-9. Our studies suggested that the balance between MMPs and tissue inhibitors of metalloproteinases (TIMPs) is a key determinant in tumor cell invasion. We now report that TSP-1 up-regulates TIMP-1 expression in both human breast and prostate cancer cell lines. The effect of TSP-1 on TIMP-1 expression was examined in human breast adenocarcinoma cell lines (MDA-MB-231) and human prostate cancer cell lines (PC3-NI and PC3-ML) treated with exogenous TSP-1. TIMP-1 expression was also examined in TSP-1 stably transfected breast cancer cell line (MDA